As integrated circuits have become increasingly dense according to Moore's Law, the automatic test equipment systems that evaluate functionality and performance, must be able to fit higher numbers of communication pathways or channels on the instrumentation boards for providing stimulus signals to and receiving response signals from the integrated circuit devices under test. These higher circuit densities have led to increasing connection densities and increasing clock speeds and decreasing circuit delay times. These performance requirements have also led to increasingly higher power densities within the circuits of the automatic test equipment systems. With no corresponding improvement for heat transfer technology as is indicated by Moore's law, the cooling demands have increased over time from natural convection in the 1970's to indirect liquid cooling using expensive vacuum-brazed cold plates of the current art.
Further the lower delay times and the higher clock rates have created signals that must be transmitted on coaxial cables or equivalent high speed cabling. The performance requirements of integrated circuits have forced the use of one or even two coaxial cables to the device-under-test. Further, these requirements have even forced the use of coaxial cables with larger conductors. The coaxial cable bundles are physically long, wide, and heavy. Timing accuracy is becoming limited by signal degradation in the path from the main electronic test control circuits to the test head which connects to the device-under-test.
The present inventor has further realized that the increasing number of channels and the performance requirements has made it impractical to continue packaging most of the test circuits that communicate directly with the device-under-test in with the main electronic test control circuits. The performance and miniaturization of transistors on integrated circuits in present and future technologies have resulted in cable challenges in the pathways between the test circuitry and the physical device interface board that receives the device-under-test. The sheer volume of several thousand 2-foot coaxial cables is causing problems for repeatably routing and restraining the mass of heavy and expensive coaxes. Design compromises between cable diameter and signal fidelity are impacting the performance of the integrated circuit automatic test systems.
Therefore, what is needed is a way to allow high performance test at high density and high clock speeds.